Received August 16, 2015; Revision received September 11, 2015
Expression and methylation patterns of genes encoding DNA
methyltransferases and their functionally related proteins were studied
in organs of Arabidopsis thaliana plants. Genes coding for the
major maintenance-type DNA methyltransferases, MET1 and CMT3, and the
major de novo-type DNA methyltransferase, DRM2, are actively
expressed in all organs. Similar constitutively active expression was
observed for genes encoding their functionally related proteins, a
histone H3K9 methyltransferase KYP and a catalytically non-active
protein DRM3. Expression of the MET1 and CMT3 genes is
significantly lower in developing endosperm compared with embryo. Vice
versa, expression of the MET2a, MET2b, MET3, and
CMT2 genes in endosperm is much more active compared with
embryo. A special maintenance DNA methylation system seems to operate
in endosperm. The DNMT2 and N6AMT genes encoding putative
methyltransferases are constitutively expressed at low levels.
CMT1 and DRM1 genes are expressed rather weakly in all
investigated organs. Most of the studied genes have methylation
patterns conforming to the “body-methylated gene”
prototype. A peculiar feature of the MET family genes is
methylation at all three possible site types (CG, CHG, and CHH). The
most weakly expressed among genes of their respective families,
CMT1 and DRM1, are practically unmethylated. The
MET3 and N6AMT genes have unusual methylation patterns,
promoter region, and most of the gene body devoid of any methylation,
and the 3′-end proximal part of the gene body is highly
methylated.
KEY WORDS: DNA methylation, DNA methyltransferase, gene
expression, quantitative PCR, bisulfite sequencing, Arabidopsis
thaliana